The above-noted, commonly-owned, related applications describe automatic mailing machines capable of handling mixed mail and capable of high-speed processing of mailpieces.
Automatic mailing machines typically include imprinting systems, such as a postage meter, where the information imprinted on the envelope or other sheet-like median is attributable to a variable parameter of the median, such as imprinting a postage value indicia on an envelope wherein the postage value is based on the weight of the envelope. In the mail processing field, it is desirable for a system operator to be able to deliver to mail processing equipment a batch of "mixed mail," that is, the batch is comprised of a large number of envelopes of varying dimensions, and variable thickness of weight. The ability of a mail processing system to process a large variety of mixed mail eliminates the need of the system operator from performing a preliminary step of presorting the mail. It is further desirable for mail processing equipment to be able to weigh the individual envelopes and affix the appropriate postage value indicia in accordance with the envelope weight. It is generally considered advantageous if the mail processing equipment can imprint a quality indicia upon envelopes varying in thickness from that of a postcard to approximately three-quarters (3/4) of an inch.
It is known to provide mail processing equipment comprised of a feeder for singularly delivering envelopes in series to a transport assembly. The transport assembly deposits the envelope on a scale for weighing. After a sufficient time to assure a true scale reading of the envelope weight, commonly referred to as "weigh on the pause", the transport assembly again assumes control over the envelope and delivers the envelope to a module commonly comprised of an integral transport assembly and attached flat bed postage meter. The mailing machine transport assembly assumes speed control over the envelope performing any necessary speed adjustments to the envelope required to match the envelope's traversing speed to the imprinting speed of the postage meter print drum to promote a quality indicia print. It is known for the postage meter to include a value setting mechanism and to adjust the postage meter printing mechanism for printing of the appropriate postage rate on the approaching envelope according to the envelope weight as determined by the scale. Reference is made to commonly-assigned U.S. Pat. No. 3,877,531 which describes in greater detail a prior art automatic mail handling machine.
It is desirable to provide a mail processing system as depicted above with (i) the capability to process a dimensionally wide variety of envelopes including thickness or weight, (ii) to do it as fast as possible in terms of envelopes per second, (iii) while applying a quality postage indicia.
The copending, commonly-owned application, Ser. No. 291,483, whose contents are incorporated herein by reference, describes a mailing machine for high-speed processing of mixed mail, capable of high throughput, and of compact size. It includes mail piece processing at four main stations or modules in a straight-through manner, under positive control at all times by separate drive units or transport means at each station, with the sequential processing actions timed to optimize mailpiece throughput. The controlling and timing is determined by signals received from a plurality of sensors distributed throughout the machine. In response to the sensor signals, a microprocessor issues drive and control signals to various operating mechanisms located at the mailpiece processing stations.
The copending commonly-owned application, Ser. No. 281,354, whose contents are incorporated herein by reference, describes a programmable microprocessor drive or motor controller and a programmable microprocessor sensor controller in communication with one another. The sensor controller is programmed to poll each of a plurality of sensors located at various places in the machine and store the sensor information until called for by the motor controller. The latter, in turn, in response to the sensor information outputs control signals along communication channels connected to a motor driver which actuates its assigned mechanism in accordance with the control information. Position servo-control and velocity servo-control, as is well known, can be incorporated in such a system. A sensor reading and motor control activating polling cycle is used, using a time-slicing cyclical approach, which is programmable, such that during each cycle, during its assigned time slice, each sensor is visited and its state read and stored. During other time slices of the cycle, motor control commands are issued. This system has the advantage that it manages time much more efficiently, which significantly contributes to the high-speed processing. Moreover, it is possible to program the microprocessors to schedule actions in different sequences for different machine modes, and to assign priorities to certain actions in order to increase the duration of the time intervals allocated to certain actions at the expense of other actions.
Despite the significant advances so far made for high speed processing of mail, these exists a continual need to improve the processing efficiency and increase the speed. A significant constraint is the limited time available to monitor the progress of a mailpiece through the machine. Individual monitoring is essential for mixed-mail processing since larger or thicker envelopes typically require different processing parameters than smaller or thinner envelopes. Moreover, in a complex machine wherein the envelope is subject to a large number of operations, e.g., singulation, thickness-measuring, flap-stripping, flap-sealing, weighing and indicia-printing, information concerning the status of the envelope at a previous station is essential for initiating actions at the next station. Hence, the machine controller must know within prescribed time intervals the status and condition of a number of machine events that are being carried out simultaneously or nearly simultaneously. As the mailpiece processing speed increases, the prescribed time intervals shrink.
A further constraint is economy. While real-time high speed monitoring might more readily be obtained with expensive, state-of-the-art computers, the costs thereof cannot be economically justified. Hence, a need exists to perform the functions above described with modestly priced controllers, typified by the 8051/8096 family. With this constraint, we have found that, to construct a sensor processing system following the teachings of the above-identified applications, creates certain problems which limits the processing speed attainable.